The invention relates to the well-known types of folding machines which are disclosed for instance in the U.S. Pat. Nos. 2,847,209 of Olson and 3,328,026 of Bartizal, Jr., in West German Patent 962,258, in East-German Patent 37,058, in the magazine "Deutscher Drucker" of Nov. 27, 1969, FIG. 22 and the appertaining text in the right hand column on the same page, as well as on page 13 of a pamphlet "entre nous" distributed by the French company Leysen & Meier S.A..
The prior-known shape of the upper and lower lips of the folding or buckling pockets as well as the space between the guide rods forming the walls of the pockets determine the accuracy of the folding. The folding accuracy is increased by guiding the paper as closely as possible between the lips and the adjoining wall portions of the pockets.
In West-German Patent 962,258 it is recommended to bring the three folding rollers cooperating with the folding pocket as closely together as possible, which requires, however, the control of the lower lip of the folding pocket. This is not only more expensive but also prevents a high rate of folding sequences.
East-German Patent 37,058 discloses a folding pocket which provides a varying adjustable spacing between the upper and lower rods forming the walls of the pocket so as to render the folding pocket adjustable for varying paper thicknesses or for single and multiple pre-folded paper layers. This pocket has a rearward portion only adjustable but the front portion of the pocket is not variable so that the adaption is ineffective for short papers to be folded. Besides, the transition region between the forward upper pocket inlet to the adjoining sheet guide is not suited to permit pre-folded sheets having a short upwardly projecting flap, acting like a grapple hook, to leave the pocket. Thus, this type of folding machine is excluded from use for this frequently occuring pamphlet folding. Moreover, the transverse waving is increased by this construction in that the forward unadjustable lips have always to be adjusted at maximum width so as to accomodate all paper thicknesses. A further very aggravating disadvantage for high-speed machines is that the upper lip has surfaces paralleling the path of the sheet, on which the fast moving sheet sliding over it may be statically charged, whereupon the magnetism produced thereby impedes the entry of the sheet, which leads to a premature or inaccurate fold.
Other known machines have the pocket formed into an upper and lower frame portion each carrying a lip and being spring biased against each other and being adjustable within certain limits by pressure screws so as also to receive heavier paper layers. Here the lips are for adjustment moved away from each other so that they have to have sufficient spacing from the folding rollers, a distance which has, however, to be kept small for bent sheets because these have the tendency to enter into any space that offers itself in bypassing the folding pocket opening. This leads to malfunctioning and stoppage.
Finally, arrangements based on machines built by the inventor himself have been sketchily published before the filing of the present application. However, these publications either do not disclose the essential features of the invention, or the authors of those publications -- the above named magazine "Deutscher Drucker" and the pamphlet "entre nous" misunderstood or did not actually know the construction or for other reasons mis-represented it so as not to teach the actual invention as it is disclosed and claimed in the present application.